Currently, sickened mobs kind of just act like retextured regular mobs (i.e sickened zombie has same AI and abilities as regular zombie). I think they should have some kind of wither ability, such as skeleton arrows are tipped with the wither effect, zombies grant wither when attacking, creepers leave a wither cloud, and spiders grant wither 2. Maybe upon being attacked they give a few seconds of wither to the attacker, or they can infect mobs with wither sickness. To prevent mod compatibility issues, there could be a config option in "common" to turn it off.

Yea Wither Sickness would be to strong.

eh, could be only on hard difficulty or smth

Maybe wither sickness or that would be too powerful.

Yea Wither Sickness would be to strong.

They already do more damage

Will be implemented in the next major release

after playing survival i regret this
but other people may hate it too so please keep the feature